code: def test_get_regressor_cols():
      """Tests get_regressor_names"""
      template = AutoArimaTemplate()
      # no regressors
      model_components = ModelComponentsParam()
      template.config = ForecastConfig(
          model_components_param=model_components
      )
      assert template.get_regressor_cols() is None
  
      model_components = ModelComponentsParam(regressors={})
      template.config = ForecastConfig(
          model_components_param=model_components
      )
      assert template.get_regressor_cols() is None
  
imports: import datetime
  import numpy
  import pandas
  import greykite.common.constants
  from greykite.common.constants import TIME_COL
  from greykite.common.constants import VALUE_COL
  from greykite.common.evaluation import EvaluationMetricEnum
  from greykite.common.python_utils import assert_equal
  from greykite.common.testing_utils import generate_df_for_tests
  from greykite.common.testing_utils import generate_df_with_reg_for_tests
  from greykite.framework.constants import COMPUTATION_N_JOBS
  from greykite.framework.constants import CV_REPORT_METRICS_ALL
  from greykite.framework.templates.auto_arima_template import AutoArimaTemplate
  from greykite.framework.templates.autogen.forecast_config import ComputationParam
  from greykite.framework.templates.autogen.forecast_config import EvaluationMetricParam
  from greykite.framework.templates.autogen.forecast_config import EvaluationPeriodParam
  from greykite.framework.templates.autogen.forecast_config import ForecastConfig
  from greykite.framework.templates.autogen.forecast_config import MetadataParam
  from greykite.framework.templates.autogen.forecast_config import ModelComponentsParam
  from greykite.framework.templates.forecaster import Forecaster
  from greykite.framework.templates.model_templates import ModelTemplateEnum
  from greykite.framework.utils.framework_testing_utils import assert_basic_pipeline_equal
  from greykite.sklearn.estimator.auto_arima_estimator import AutoArimaEstimator
label_desc: Use image node_id 2 for calling a global function with example usage: test_get_regressor_cols() without return types